Low volume insecticide aerosol generator

ABSTRACT

A method of producing an insecticide spray for killing insects with droplets in the size range of from about 5 microns to about 15 microns. The spray consists of an insecticide, such as Naled14, diluted with a non-volatile liquid, such as cottonseed oil, in a ratio of 1 to 4 by volume. The aerosol generating equipment includes an engine driven blower supplying air at about 450 cubic feet per minute at a pressure of about 4 psi. This air is supplied to a group of four air-liquid double vortical nozzles that atomizes the insecticide into the 5 to 15 micron size range.

United States Patent 1191 Stains 1451 Feb. 26, 1974 LOW VOLUMEINSECTICIDE AEROSOL GENERATOR [76] Inventor: George S. Stains, 45-655Mohawk Cir., Indian Wells, Calif. 92260 [22 Filed: July 2, 1971 21 Appl.No.: 159,318

Related US. Application Data [62] Division of Ser. No. 8,574, Feb. 4,1970, Pat. No.

[52] US. Cl. 43/124 [51] Int. CL... A01m 7/00 [58] Field of Search43/131, 129, 124, 125;]

[56] References Cited UNITED STATES PATENTS 3,239,960 3/1966 Stevens43/129 3,200,535

8/1965 Hession, Jr. 43/129 3,636,207 Bouvet et a1 43/131 2,971,8822/1961 Ospenson et al. 424/225 3,595,958 7/1971 Koundakjian et al424/225 3,630,446 12/1971 Strengelbach et al. 43/131 PrimaryExaminer-Warner H. Camp Attorney, Agent, or Firm-R. S. Sciascia; CharlesD. B. Curry [57] ABSTRACT A method of producing an insecticide spray forkilling insects with droplets in the size range of from about 5 micronsto about 15 microns. The spray consists of an insecticide, such asNaled-14, diluted with a nonvolatile liquid, such as cottonseed oil, ina ratio of l to 4 by volume. The aerosol generating equipment includesan engine driven blower supplying air at about 450 cubic feet per minuteat a pressure of about 4 psi. This air is supplied to a group of fourair-liquid double vortical nozzles that atomizes, the insecticide intothe 5 to 15 micron size range.

5 Claims, -'2 Drawing Figures LOW VOLUME INSECTICIDE AEROSOL GENERATORThis is a division of application Ser. No. 8,574, filed Feb. 4, 1970 byGeorge S. STAINS and now US. Pat. No. 3,648,401.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

Much of the currently available insecticide dispensing equipmentproduces relatively large droplets which, for many purposes, isinefficient and ineffective. For example, 95 percent or more of theinsecticide dispersed is in the droplet size range of from 50 to 400microns and is largely wasted since the majority of it rapidly settlesout by normal gravitational pull in a relatively short distance. It hasbeen found with equipment of this type that the effective swath killdoes not exceed about 600 feet. Much of this equipment utilizes exitvelocity for dispersal of the droplets.

The present invention overcomes this difficulty by producing insecticidedroplets of a size range of from about microns to about microns with amass median diameter of less than 10 microns. The importance of thisreduction in size will be apparent by comparing the number of dropletsdispensed with conventional equipment to that dispensed by the equipmentof the present invention. That is, in a milliliter of liquid there willbe produced about 2,000,000 droplets of 100 micron diameter as comparedto about 9,000,000,000 droplets of 6 microns diameter, or a 5,000 foldincrease in number of 6 micron size droplets in the same amount ofmaterial. From this it can be seen that there is a much greaterprobability of an insect coming in contact with the smaller sizeddroplets as compared to the larger sized droplets. However, it has beenfound that there are certain limits as to how small the droplets can bemade and still be effective. It has been found that the minimum size ofdroplet for flies and mosquitoes is about 3 to 5 microns. This isbecause the air current surroundingthe insects will cause very smalldroplets to be carried by the air current around the insect and therebynot come in contact with the insect. With a 5 micron droplet it has beenfound that the momentum of the droplet will-cause it to strike theinsect, or the insect to strike it, without being carried around theinsect by the air currents.

Another aspect of the present invention is the discovery that there isabout 4 times as much insecticide, when using Naled-l4 insecticide, forexample, in a 5 micron droplet than is necessary to kill a fly or amosquito. Therefore, a given volume of Naled-14 insecticide, forexample, may be diluted with a liquid. It has been found that anon-volatile liquid has definite advantages for this purpose. This isbecause, if a volatile liquid were used, the 5 micron droplets wouldevaporate down to a smaller size and not have sufficient inertia orweight to penetrate the air stream surrounding the insects. Cottonseedoil has been found to be very effective for this purpose, not onlybecause it is nonvolatile, but because it is relatively inert and willnot attack paints and the like with which it may come in contact in thetarget area. The practice of the present invention has provided swathsthat kill flies and mosquitoes in excess of 2 miles from the source.

Briefly, the present invention comprises a method of producing aninsecticide spray for killing insects with droplets in the size range offrom about 5 microns to about 15 microns. The spray consists of aninsecticide, such as Naled-l4, diluted with a non-volatile liquid, suchas cottonseed oil, in a ratio of I to 4 by volume. The equipment used togenerate the spray comprises an engine driven air blower that suppliesair at about 450 cubic feet per minute and at about 4 psi pressure to amanifold. The air manifold houses four air-liquid double vortical typenozzles which are surrounded by the high volume pressurized air. Theengine also drives an air compressor pump that supplies air topressurize the insecticide reservoir. The insecticide passes through ateflon and stainless steel conduit having a stainless steel cutoff valveand a stainless steel calibrated metering valve into the four air-liquidnozzles. The nozzle assembly, working on a double internal vortex typeventuri principle, creates controlled turbulence. The pressurized air inthe manifold enters the lower vortical disk creating a spiral patternwhirling through the central mixing chamber in a clockwise direction. Astream of liquid is injected at 30 to 60 psi through an orifice and intothese two opposing air turbulences and is sheared off at the sharp edgeof the forward end of the mixing chamber and thereby breaking up theinsecticide into droplets having a size range of from about 5 to about15 microns diameter.

Other objects, advantages and novel features of the invention willbecome apparent from the following detailed description of the inventionwhen considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a schematic diagram of the insecticide aerosol producingapparatus used in practicing the present invention; and Y FIG. 2 is anenlarged sectional view taken at 22 of FIG. 1.

In FIG. 1 is shown a schematic diagram of the aerosol generator 11 usedto generate the aerosol spray in accordance with the present invention.Aerosol generator 11 includes a motor 13, such as a 14 HP four cyclegasoline engine, that drives output shaft 15 through clutch assembly 17.A clutch assembly is optional and normally would not be included if theengine is equipped with a starter/generator combination. Rigidlyattached to output shaft 15 are drive pulley l9 and dual drive pulleys21. Air compressor 23 includes an air inlet 24, an input shaft 25, apressure relief valve 27 and an out let conduit29. A flexible frictionbelt 31 interconnects pulley 19 with pulley 33 that is'connected toshaft 25 of the compressor.

The air from compressor 23 passes through conduit 29 to the upper regionof reservoir 35 that contains the liquid insecticide 37 that is to besprayedReservoir 35 includes a pressure relief valve-39, a pressuregauge 41 and an outlet conduit 43. A high flow rate air blower 45includes an input shaft 47 having a dual drive pulley 49 attachedthereto that is driven by motor l3 by dual friction belts 51. Blower 45also includes an air inlet 53 and an air outlet conduit 55. j I

Aerosol generating manifold 57 includes an elongated manifold conduit59, about 30 inches long, having a generally circular cross-section,about 5 inches in diameter, that is closed at both ends. Included withinI 35 through conduit 43 having cutoff valve 69 and metering valve 71. Ahigh volume source of air is supplied to the interior region of manifoldconduit 59 by conduit 55 wherein the air completely surrounds nozzles 61through 64 and is used to mix with and atomize the insecticide.

In FIG. 2 is shown an enlarged sectional view taken at 22 of FIG. 1.Nozzle 62 is supplied insecticide from conduit 67 through flexibleconduit 73. Nozzle 62 includes a first air inlet section 75 and a secondair inlet section 77. Air inlet 75 includes curved vanes that cause theinlet air passing therethrough to form into a vortex 79 having aclockwise direction of rotation. Air inlet 77 includes curved vanes thatcause the inlet air passing therethrough to form into a vortex 81 havinga counterclockwise direction of rotation. The liquid insecticide passesthrough inlet conduit 83 and is then mixed in chamber 85 with clockwiserotating air vortex 79. The mixture of air and insecticide generated inchamber 85 is then mixed with the counterclocking air vortex 81 as itdischarges from the end of chamber 85. This causes extreme agitation andshearing of the insecticide into droplets having a size range of fromabout 5 to about 15 microns diameter.

The operating parameters of the system as successfully employed are asfollows: The pressure of the supply air within manifold conduit 59 isfrom about 3 /2 to about 4 psi above atmospheric pressure. The air flowrate through all four nozzles 61 through 64 is about 450 cubic feet perminute and is normally held constant. The flow rate of insecticidethrough all four nozzles is from about to about 100 ounces per minutewherein the rate is controlled by metering valve 71 of FIG. 1. At lowerinsecticide flow rates the majority of the insecticide is formed intodroplets having a size of order of about 5 microns and at high flowrates the majority of the insecticide has a droplet size that is of theorder of about microns. However, at both the low and high flow rates atleast about 95 percent of the insecticide is formed into droplets withinthe 5 micron to 15 micron range. The insecticide is preferably dilutedwith a diluent such as cottonseed oil or one of the other vegetableoils. The ratio of diluent to insecticide is determined by theinsecticide'heing used. An effective spray has been found to compriseNaled-l4 diluted with cottonseed oil in a ration of l to 4 by volume.The use of non-volatile cottonseed oil prevents. the diluent in thedroplets from evaporating and causing the droplet to reduce in size andthereby prevents its loss of effectiveness by drifting around theinsects in the air'currents surround the insects. What is claimed is:

l. A method of producing a chemical spray wherein at least about percentof the spray comprises droplets in the size range of from about 5microns to about l5 microns in diameter consisting of:

a. passing a high volume of air at an elevated pressure of approximately4 psi at approximately ambient temperature into a mixing chamber;

b. simultaneously directly introducing a liquid chemical solution intosaid mixing chamber; and

c. creating a turbulance in the air flow through the chamber and therebycausing a breakup of the liquid solution prior to discharge from themixing chamber.

2. The method of claim 1 wherein:

a. said turbulance is created by generating an air vortex of the airpassing through the mixing chamber.

3. The method of claim 2 wherein:

a. said turbulance is intensified by creating a second air vortex havinga direction of flow opposite to said first mentioned air vortex.

4. The method of claim 1 wherein:

a. said spray is intended for the purpose of killing insects such asmosquitoes and flies; and

b. said liquid chemical solution comprises 1 part by volume of activeinsecticide and 4 parts by volume of a non-volatile liquid.

' 5. The method of claim 4 wherein:

a. said insecticide comprises NALED-l4; and

b. said non-volatile liquid comprises cottonseed oil.

2. The method of claim 1 wherein: a. said turbulance is created bygenerating an air vortex of the air passing throUgh the mixing chamber.3. The method of claim 2 wherein: a. said turbulance is intensified bycreating a second air vortex having a direction of flow opposite to saidfirst mentioned air vortex.
 4. The method of claim 1 wherein: a. saidspray is intended for the purpose of killing insects such as mosquitoesand flies; and b. said liquid chemical solution comprises 1 part byvolume of active insecticide and 4 parts by volume of a non-volatileliquid.
 5. The method of claim 4 wherein: a. said insecticide comprisesNALED-14; and b. said non-volatile liquid comprises cottonseed oil.